A real-time test system software under Windows platform is designed and realized by utilizing the technique of multithreading in this paper. First, combined with the examples, the general block diagram and thinking of real-time test system software are introduced after analyzing multithreading and its synchronization mechanism. Second, the concrete realization method of the system software based on synchronization event object is described. And last, the work flow of multithreading in the road surface roughness laser test system software is provided in detail. The above method, thinking and work flow have been fully applied to the development of the road surface roughness laser test system software, from which good results are achieved.